Question

Range of frequency of audible sound is ______Hz to _____Hz.
A. 20, 20000
B. 10, 20000
C. 30, 30000
D. 2, 2000

Answer 1

Hint: Audible range for the human ear is just above the infrasound range to just below the ultrasound range.

Complete step-by-step answer:
To understand the frequency range and various frequencies that are there in nature, we need to know what is the pitch of the sound. The pitch of a sound wave corresponds to the number of times the wave repeats itself in a certain period of time. Hence, when we say low pitched noise, what we can understand is that it has a large time period or the medium producing it is vibrating very slowly. Similarly, when we say high pitched noise, we mean that the medium producing that wave is vibrating very quickly causing rapid waves formation known as the high pitched sound.

1.) Infrasound wave: This sound or wave refers to the low pitched sounds. Here the intervals between the beats of source medium are very large. All waves below 20Hz are known as infrasound waves. An example would be, consider a drum being hit very slowly after considerable amounts of time. It’s necessary to hit very slowly, since the drum membrane vibrates which produces the sound and hitting the drum hardly will cause the membrane very quickly causing higher pitched sound instead of low pitched sound. Naturally, the movements of the earth’s plates also produce infrasound which are sensed by animals giving them an early warning. Additionally, bats also produce infrasound.

2.) Ultrasound wave: This sound or wave refers to very high pitched sounds. Here the intervals between the beats of the source medium are extremely small. They are so small that it’s almost impossible to distinguish the beats from each other. Here, the source medium oscillates immense number of times to generate an ultrasound wave. All waves having frequency above 20kHz are known as ultrasound waves. Ultrasound waves are produced by oscillating materials in the ultrasound frequency range to produce corresponding frequencies which are used to find flaws in metals. Since, the ultrasound frequency is very large as compared to the natural frequency of most metals, the ultrasound frequencies can travel within the metal easily.

Hence, upon encountering any flaw in the metal, it reflects back abruptly giving information about the location of the defect as well.

Hence, Human ear’s audible range is from 20Hz to 20,000Hz.

Note: Important takeaway here is that the starting frequency is at 20Hz, not a very small frequency.
The upper cutoff frequency is 20kHz, same as the lower cutoff frequency multiplied with 1000.